A Mexican citizen, said to be in this country illegally, was arrested on suspicion of manslaughter and hit-run driving after an accident that left an off-duty police officer dead and the officer’s wife in a coma. Pomona police said a car driven by Juan Manuel Alvarado, 32, ran a stop sign and crashed into an automobile driven by Linda Vasquez, 27, in which her husband, Officer Geronimo Salazar Vasquez, 41, was a passenger, at 9th and Palomares streets, overturning the Vasquez vehicle. Vasquez died at Pomona Valley Community Hospital where his wife was reported in critical condition. Alvarado fled the scene on foot, police said. But the abandoned car was traced to Alvarado, who was arrested a few hours later at the home of a relative in Lynwood.